According to a known method of manufacturing a ceramic green body, a ceramic slurry containing a ceramic powder, a dispersion medium, and a gelling agent is subjected to molding in a mold, and the resultant molded product is released from the mold, whereby a ceramic green body is obtained. This manufacturing method is a so-called gelcasting process. Conventionally, a method of manufacturing a solid ceramic green body by gelcasting has been proposed (in, for example, Japanese Patent Application Laid-Open (kokai) No. H01-261251). Also, a method of manufacturing a hollow ceramic green body, or a ceramic green body having a cavity therein, by gelcasting has been proposed (in, for example, Japanese Patent Application Laid-Open (kokai) No. 2002-216626).
The methods of manufacturing a ceramic green body proposed in the above-mentioned Patent Documents are gelcasting processes that employ a special ceramic slurry as a molding ceramic slurry, and are adapted to manufacture a ceramic green body having a complicated shape or structure at high dimensional accuracy.
According to a method of manufacturing a ceramic green body by gelcasting, a ceramic green body having a complicated shape or structure can be manufactured at high dimensional accuracy. However, even in such a ceramic green body, presence of slight damage, such as cracking, is not permitted. Presence of even slight damage to a ceramic green body has an adverse effect on the mechanical strength and thermal strength of the ceramic green body. Particularly, when the ceramic green body is to be fired into a sintered product, even such slight damage may cause breakage of the body during firing, potentially resulting in a failure to manufacture a sintered product from the ceramic green body.
A cause for occurrence of slight damage, such as cracking, to a ceramic green body is shrinkage of the ceramic green body during molding or unsmooth release of the ceramic green body form a mold. The methods of manufacturing a ceramic green body proposed in the above-mentioned Patent Documents do not give any consideration to elimination of such a cause.
Particularly, a mold for forming a hollow ceramic green body includes an outer mold formed from an unmeltable material and a core formed from a meltable material. The core is contained in the outer mold so as to form a predetermined cavity between the same and the outer mold. A green body is formed within the mold in such a manner as to contain the core therein. Accordingly, the green body must be released from both the outer mold and the core.
In order to facilitate release of a green body from the core, the core is formed from wax, which is readily melted at low temperature. In removal of the green body from the core, the core contained in the green body is thermally melted. The molten core is ejected from the interior of the green body. This releasing procedure potentially involves the following problem: when the core is thermally melted, a thermal expansion force acts on the green body and causes occurrence of damage, such as cracking, to the green body.